Extruded article and method of making same

ABSTRACT

An extruded article is provided comprising a base element, and at least one rib element attached to the base element along its entire length. The rib element is narrower at its attachment end than at its free end, and is undulated. 
     The article is formed by extruding an extrudable plastic mass having a conformable state and a nonconformable state. The extrusion rate of the free end of the rib element is sufficiently faster than that of the base element. The free end of the rib element will therefore undulate as the structure is extruded. The free end of the rib element is permitted to undulate without distortion of the base element while the plastic mass is in the conformable state. The plastic mass is then converted to the nonconformable state while maintaining the undulation in the free end of the rib element.

DESCRIPTION

1. Technical Field

The present invention relates to an extruded article having anon-uniform undulating rib structure on one or both sides of the articleand a process for extrusion of the article by a direct extrusion processwith an extrusion die having no mechanical moving or reciprocatingparts.

2. Background Art

Various three dimensional plastic networks find utility in a widevariety of applications. For example, a three-dimensional web which maybe formed of crimped staple fibers adhered together at points of contactor of extruded, autogenously bonded, continuous filaments. The webs maybe employed as the structural element of a non-woven abrasive pad orarticle. Additionally, the same fiber or filament structures and otherthree-dimensional open plastic networks such as reticulated foams may beemployed as filters, mats for cushioning, wiping, or any of a widevariety of other uses.

Various methods of making three-dimensional structures of variousmaterials such as plastics are known in the art. U.S. Pat. No. 4,332,757(Blackmon), discloses the preparation of a textured continuous filamentyarn made by combining molten streams of polymer in a side-by-sideconfiguration with one stream at a higher speed than the other to createa yarn with a false twist.

U.S. Pat. No. 4,384,022 (Fowler), assigned to the assignee of thepresent application, discloses a filamentary structure comprising athermoplastic core filament extending in successive turns of spiral andthermoplastic sheath filaments which extent linearly generally in thedirection of the axis along the outside of the spiral. The structureformed by this disclosure, however, cannot include a core filamenthaving an aspect ratio much greater than one in order to maintain thespiral.

U.S. Pat. No. 3,178,328 (Tittmann) discloses a process and apparatus forproducing a plastic net utilizing a die having an oscillating portion toextrude linear filaments, together with oscillating filaments to createa sine wave in the oscillating filaments, thereby creating a net-likestructure. Tittmann's disclosure fails to indicate that anything otherthan a flat plastic net may be produced.

U.S. Pat. No. 3,193,604 (Mercer) teaches the ability to form an extrudedsheet having ribs on both sides of the sheet by using a reciprocating orrotating extrusion die. The ribs on any given side may intersect or joineach other depending on the rib spacing and the amplitude of the riboscillation.

U.S. Pat. No. 4,233,259 (Pietratus) teaches the method of extrusion of asingle inverted "T" (cross section) element or strand of which theupward leg undulates to form an untapered "wavy fin". The undulation iscaused by having a shorter length of the approach surface leading to thefin profile opening in the die than that leading to the base opening.This causes areas of higher flow velocity which in turn results in anincreased supply of the material to be extruded to these regions of theprofile openings. The patent also teaches the need for a guide platenear the orifice exit to control width and/or change the direction ofthe fin folding.

U.S. Pat. No. 4,419,315 (Kessler) teaches the extrusion of aweatherstrip comprising a plurality of thin untapered flexible ribs in awavy pattern that is attached to a backing strip from the same extrusionprocess. Straight and sinusoidal rib combinations are also disclosed.Kessler's disclosure fails to reveal ribs with non-uniformcross-sectional profiles.

U.S. Pat. No. 4,631,215 (Welygan), assigned to the assignee of thepresent application, discloses an extruded article comprising aplurality of linear spaced parallel extruded filaments separated by aregularly folded undulated extruded element having an aspect ratio of atleast about two. The undulations have opposed apexes on either sidethereof with apexes on one side of the undulated elements being bondedinitially without adhesive to one of the parallel extruded elements andthe apexes on the other side of the undulated element being bonded tothe other parallel extruded element.

DISCLOSURE OF THE INVENTION

The present invention provides a unique extruded article having a baseelement and at least one undulating tapered rib element. The rib elementis attached to the base element along its entire length. The article mayhave multiple tapered rib elements and may also have secondarystructures, i.e., nontapered rib elements interspersed therewith.

More particularly, the extruded article of the present inventioncomprises an elongate base element, and at least one elongate ribelement having an attachment end and a free end, the attachment endbeing attached to the said base element along its entire length and therib element being narrower at its attachment end than at its free end.The rib is the same length as the base element at its attachment end,being longer and undulated at its free end.

The invention is not limited to articles having planar base elements butmay comprise articles with base elements having a corrugated appearanceor circular or tubular cross-sections. The ribs may be separated fromeach other or they may touch each other. It is possible to mix ribshaving different amplitudes and/or different frequencies of undulationand different heights. The ribs may be interspersed with extrudedstraight elements or other profiles in any combination. These straightelements may also be attached to the base element but this is not arequirement.

The article is formed by the following steps: (a) extruding anextrudable plastic mass having a conformable state and a cured state toform an elongate extruded structure having a base element and at leastone elongate rib element having an attachment end and a free end, withthe attachment end being in contact with the base element along itsentire length. The rib element is narrower at the attachment end than atthe free end; the extrusion rate of the base element and the attachmentend of the rib element is the same but is sufficiently slower than theextrusion rate of the free end of the rib element so that the free endof the rib element will undulate as the structure is extruded. The freeend of the rib element is permitted to undulate without distortion ofthe base element while the plastic mass is in the conformable state. Theplastic mass is then converted to the cured state while maintaining theundulation in the free end of the rib element.

As used herein, the term "extrudable plastic mass" refers to a substancehaving a viscosity which permits it to be extruded as a filament,ribbon, film or the like from an extrusion orifice and, upon extrusion,will have sufficient cohesiveness to maintain its extruded shape for afinite period of time to permit subsequent process steps.

The current invention is not restricted to thermoplastic materials. Anyorganic or inorganic material possessing viscoelastic characteristicscan be used; this includes materials wherein such characteristics arepresent in an intermediate stage. Such materials need only maintain theextruded shape long enough to permit any necessary subsequent processsteps such as drying, firing, freezing or hot oil setting.

Examples of substances which will provide a filament-forming extrudableplastic mass for use in the present invention include:

(a) Synthetic thermoplastic resins capable of melt extrusion orcompression extrusion in a molten state through dies and settable oncooling after extrusion. Readily obtainable suitable thermoplastcmaterials include polyamides or super polyamides (e.g., nylon),polyesters, polyurethanes, vinyl polymers (e.g., vinyl acetatepolymers), vinyl chloride polymers, polyvinyl chloride and copolymersthereof with other ethylenically unsaturated monomers such as vinylacetate, vinylidene chloride, and like monomers, polyethylene,polypropylene, and thermoplastic rubbers, and the like, polyolefinpolymers, and polystyrene;

(b) Natural and synthetic rubbers, subsequently vulcanized or containingvulcanizing agents;

(c) Thermosetting plastic materials or mixtures thereof withthermoplastic materials, which are capable of extrusion in a liquid orsemi-liquid state;

(d) Natural and synthetic fiber-forming materials extruded from solventsolution, such as cellulose or protein material, cellulose acetate,acrylate polymers, as well as many thermoplastic resins as mentionedabove, dissolved or dispersed in a solvent and capable of extrusion andsetting by drying (e.g. by solvent evaporation), immersion in orspraying with a coagulant as the plastic mass emerges from the dies;

(e) Blends such as masses which may include pulverized slurriedfoodstuffs, dissolved or molten foodstuffs such as sugar-based mixtureswhich on setting form solid or resilient candy;

(f) Foamable compositions containing any of the above materials; and

(g) Any other plastic masses which may be extruded through a die to formfilaments.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention may be more clearly understood by reference to thedrawings, wherein:

FIG. 1 is a side elevational view of an extrusion apparatus for carryingout the method of the present invention located over a tank of coolingmedium and having associated therewith apparatus for removal of theextruded web from the cooling medium;

FIGS. 2 and 3 are side elevation views of alternative extrusionapparatus for practicing the method of the invention;

FIG. 4 is a representative of the opening of an extrusion die of thetype useful for preparing the article of the present invention andpracticing the method of the current invention;

FIGS. 5 and 6 are representations of die designs for making specificarticles of the invention;

FIG. 7 is a top plan view of an extruded article made in accordance withthe present invention by employing a die of the design type pictured inFIG. 6; and

FIGS. 8-22 depict cross-sectional views of exemplary alternativeextruded articles made in accordance with the invention.

DETAILED DESCRIPTION OF THE INVENTION

As shown in FIG. 1, an extrudable plastic mass is extruded by extruder10 (where the extruded substance may be rendered plastic) from extruderdie 11 which has the appropriate extruder surfaces 12 to form asubstantially continuous extruded web 13. Various methods of handlingweb 13 are possible as depicted in FIGS. 1, 2 and 3. As shown in FIG. 1,the extruded web may be formed into quench bath 14 containing a suitablequench medium such as water and guided therein by idler roll sets 15 and16 and removed therefrom by passing between idler roll set 17 afterwhich it could be wound for storage or incorporated into a product.

As shown in FIG. 2, it is also possible to maintain the extruded web ina straight configuration employing an air or water spray quench chamberfitted with appropriate idler roll sets 21. Furthermore, as depicted inFIG. 3, the extruded web may be deposited onto a continuous cooling belt10 which is preferably porous to provide dissipation of heat and passageof forced air, if desired.

FIG. 4 depicts a typical extruder die configuration having an openingcapable of extruding the simplest extruded article of the presentinvention; a single rib element 41 attached to a planar base element 42.

Various modifications of the extruded structures obtained by the presentinvention depend substantially on the extrusion slot dimensions, i.e.,the width of the rib element.

FIG. 4A depicts a cross-sectional view of an article extruded by the dieof FIG. 4 consisting of a single rib element 41 attached to a planarbase element 42.

FIG. 5 depicts a similar die. The width (cross-web) of the base element50 has two effects on the article; damping and attachment. The widthshould be selected such that it provides enough mechanical damping sothat the force of the extruded rib to bend into the plane of the backingwill not cause the entire structure to end away; rather the rib willdeflect. It is also possible to temporarily apply a retarding surface tothe back of the base element (moving belt or rotating cylinder) tominimize the mass effect of this damping such that the base may besubstantially thinner than the attached ribs. The second effect of thebase width is to provide a point of attachment which moves at a slowervelocity than the free end of the rib which is the faster movingportion. It is this differential of velocity, in combination with thebacking inertia that causes the rib to undulate.

The velocity differential may be achieved by a variety of methods, thesimplest of which is a specially designed die having an appropriateprofile. A simple profile which is easy to fabricate is a uniformlytapered slot as in FIG. 5 where 52 is the width of the rib orifice(W_(b)) at the point where the tapered slot communicates with the secondslot to form the point of attachment, and 53 is the width of the riborifice at the point on the tapered slot which forms the free end of therib (W_(t)). Although the taper of the rib element shown is a simplelinear taper, it may also be a more complex shape, e.g. a parabolic orother variable curvature as long as it produces a rib wherein the areaat the free end of the rib is greater than that at the attached end. Adie which causes a minimal velocity distribution would produce anextruded rib having little tendency to undulate. Such a rib wouldextrude simply as a straight rib while a higher velocity distributiondie will form a rib which undulates easily. This phenomenon can becharacterized by considering the ratio of W_(t) to W_(b), where a ratioof 1 reflects no tendency to undulate, and a ratio of greater than 1reflects a tendency to undulate. Larger ratios will yield largerundulation amplitudes when base thickness is held constant.

Table I shows the effect of various W_(t) /W_(b) ratios on rib amplitudefor a polyvinyl chloride structure where the rib height and basethickness are held constant:

                  TABLE I                                                         ______________________________________                                               Material: polyvinylchloride                                                   Temperature:                                                                            155° C.                                                      Rib Height:                                                                             0.559 mm.                                                           Base thickness:                                                                         0.45 mm.                                                     W.sub.t /W.sub.b                                                                          W.sub.t (mm)                                                                           Rib Amplitude (mm)                                       ______________________________________                                        1.00        0.45     0.45*                                                    1.11        0.50     0.51*                                                    1.30        0.59     2.54                                                     1.44        0.66     3.43                                                     1.66        0.76     4.57                                                     2.00        0.91     4.95                                                     2.77        1.97     5.97                                                     4.00        1.83     5.59                                                     ______________________________________                                         *no undulation; figure reflects thickness of ribs only.                  

When the W_(t) /W_(b) ratio is small, i.e., 1.0 to 1.1, the profileessentially extrudes statically with no tendency for undulation. Oncethe ratio exceeds 1.1, in this case 1.3, the dynamic phenomenon ofundulation occurs with increasing W_(t) /W_(b) ratio influencing theamplitude of the undulation.

FIG. 6 depicts a die opening for an article comprising multipleidentical rib elements attached to a planar base element.

The rib heights can also be varied and interspersed in any order. Theeffect of rib heights will also affect the frequency of undulation if aconstant taper angle is considered. This is a result of the differentialflow rate that can be achieved by either a tall rib or a short rib. Theshorter rib will result in less differential flow relative to the baseelement if there is no compensating change in taper angle.

The data in Table II illustrates that there is also a minimum rib heightrequired for undulation to occur with a constant taper angle.

                  TABLE II                                                        ______________________________________                                        Material:          polyvinylchoride                                           Temperature:       155° C.                                             Base element thickness:                                                                          0.46 mm.                                                   Taper angle:       4.2°                                                            W.sub.t                                                           Rib Height (H,mm)                                                                         (mm)    Amplitude (mm)                                                                             H/W.sub.b                                                                           W.sub.t /W.sub.b                       ______________________________________                                        0.91        0.589    0.50*       2.0   1.28                                   1.97        0.655    1.27**      3.0   1.43                                   1.83        0.721   2.79         4.0   1.57                                   2.74        0.859   4.44         6.0   1.87                                   4.57        1.123   4.95         10.0  2.45                                   5.58        1.270   5.97         12.2  2.77                                   ______________________________________                                         *no tendency for undulation; figure reflects thickness of rib only            **very slight undulation                                                 

Minimal undulation will occur when the rib height is less than 3 timesthe base element thickness.

When the rib height ratio (H/W_(b)) is low; i.e., twice the thickness ofthe backing (H/W_(b) =2.0) or less, the profile essentially extrudesstatically with no tendency for undulation. When the rib height ratio isincreased to 3 times the width of the backing, a very slight tendencyfor undulation is observed. When the rib height ratio exceeds 3.0,undulation occurs. Increasing height (and corresponding W_(t) /W_(b)increases) continues to influence the amplitude of the undulation.

FIG. 7 is a top plan view of the end section of an article produced by adie of the design of FIG. 6.

FIG. 8 depicts a cross-sectional view of an article of the inventionwith a planar base element 80 and multiple undulating ribs 81 having thecharacteristic non-uniform profile of the invention and multiplesecondary ribs 82 having uniform profiles interspersed therebetween.

FIG. 9 depicts a cross-sectional view of an extruded article of theinvention, made by the process of the invention wherein the article hasa planar base element 90 and multiple undulating ribs 91. These ribshave an area of increased taper 92 at the distal end of the rib elementfrom the base element.

FIG. 10 depicts a cross-sectional view of an extruded article having aplanar base element 100 and multiple ribs 101 attached thereto, whereinthe ribs have a circular shape 102 at the free end of the rib caused bya circular opening in the rib forming element of the die distal to thebase element forming portion.

FIG. 11 depicts a cross-sectional view of an article which also employsa circular shape on its ribs 110, however, it is positioned at themidpoint of the ribs rather than at its free end.

FIG. 12 shows a cross-sectional view of an extruded article of theinvention, having undulating ribs with a triangular or "arrowhead" shapeat the free end 121 and secondary characteristic tapered ribs 122 onboth surfaces of the base element 120. This configuration providesgreater surface area at the rib's free end if needed, e.g., if bondingof the free end of the ribs to another set of ribs is desired. Thisarticle may be formed by specific die design wherein the die has atriangular shaped opening in the rib forming element distal to the baseelement. Various shapes may be created as desired.

FIG. 13 depicts an extruded article of the invention with a planar baseelement 130 which has multiple rib elements 131 attached to each of itstwo opposite surfaces.

FIG. 14 depicts the cross-section of an extruded article of theinvention wherein the base element 140 is non-planar having a circularprofile with attached undulating rib elements 141.

FIG. 15 depicts a cross-sectional view of an extruded article of theinvention wherein the base element is a single point 150 having multipletapering rib elements 151 attached thereto.

FIG. 16 through FIG. 18 depict cross-sectional views of extrudedarticles of the invention with planar base elements having multipleattached ribs, the rib elements having one or more secondary ribsattached thereto wherein the secondary ribs have an attachment end and afree end, the attachment end being narrower than the free end, andattached to the rib element along its entire length.

FIG. 19 depicts the cross-section of an extruded article of theinvention having a base element with a nonplanar surface 190 withmultiple attached undulating ribs 191. The non-planar surface improvesintegrity of the attachment of the rib to the base element by providingadditional reinforcement at the attachment end of the rib where it isthinnest. This becomes particularly important where an article includingthis type of structure is subjected to repeated flexing, e.g., if itwere used as a floor mat. The contours of the non-planar base elementalso help ensure uniformity of rib amplitude by providing a restrainingelement near the base of the undulation so that the free end of the ribswill not overly undulate or create irregularities in amplitude.

FIG. 20 uses both a planar base element 200 and a base element with anon-planar surface 201, to combine the advantages of a base element witha non-planar type surface with the convenience of a planar base element.

FIG. 21 depicts a cross-section of an extruded article of the inventionwherein the rib element has a hollow core 210. This variation can becreated by specific die design.

FIG. 22 depicts a cross-section of an extruded article of the inventionwith a planar base element 221 having multiple groups of undulating ribelements 221 with a common point of attachment 222 to the base element.

Almost any thermoplastic material may be utilized to form the extrudedarticle of the present invention. Useful thermoplastic materials includepolyolefins, polyamides, thermoplastic polyurethane, polyesters,thermoplastic rubbers, polyvinyl chloride, polysulfone, polyimides,polycarbonates and acrylics. Low melt viscosity materials may beutilized to prepare extruded articles including a relatively smallamplitude undulation in the rib element but such materials wouldgenerally be undesirable for making articles with very large amplitudeundulation in the rib element. In general, a higher melt viscositythermoplastic material tends to be more amenable to a wide variety ofsize ranges.

It is also possible to control the melt viscosity of the thermoplasticmaterials by control of the extrusion temperature. Typically, theextrusion temperatures are selected toward the lower limits of theprocessing temperature range of the polymer. Too high a temperature mayrestrict the polymer's utility to smaller size extruded structures.Blends of materials and material compounding offer other alternative tocontrolling the melt strength. Extremely high melt viscosities may causeexcessive die swell of the extrudate, i.e., expansion of the extrudedelement upon exiting the die, and, therefore, may limit their use tostructures of large diameters.

As previously mentioned, the filament forming extrudable plastic mass isnot restricted to thermoplastic materials, although they are preferred.Useful extrudable materials also include extrudable food compositions(i.e., pasta, candy formulations, cereal compositions and the like),dissolved cellulose slurry, and other extrudable masses.

The extruded article, after extrusion, is converted by a suitabletechnique to a state where elements no longer bond to one another,hereinafter called the cured state. Such techniques, besides cooling orfreezing, could involve drying, infrared or hot oil setting, radiofrequency (RF) or microwave drying, and the like. Heat setting or curingof a thermosetting resin such as a thermosetting polyurethane willprovide one means of converting or changing the plastic mass to thestate where elements no longer bond to one another. The process may alsobe utilized to extrude articles from inorganic extrudable masses such asthose utilized for the formation of ceramic materials. Such articleswould, of course, require drying and firing.

The dies useful in the preparation of the extruded articles of thepresent invention are relatively simple, merely having the appropriateorifices prepared by machining or drilling.

The preferred range of die size for the current invention consists ofrib heights varying from about 1.25 mm to about 26.0 mm. The rib widthcan vary from about 0.25 mm to about 6.50 mm. The preferred W_(t) /W_(b)ratio is from 1.5 to 3.5 although this ratio is very dependent on theend article configuration. The rib spacing can vary from 0.75 mm (thelower limit is that point where a rib can be formed which does not touchits nearest neighbor during extrusion but allows a minimum of undulationto about 12.5 mm. The dies can be fabricated using standard engineeringpractices with a die length to diameter ratio (L/D ratio) in the 5 to 10range. A lower L/D ratio causes increased die swell in the product whichis not desirable. FIG. 4 illustrates a typical die configuration withstreamlined entrance region to minimize flow deadspots.

Die width can vary from a single element to over 1.5 meters. The die mayalso include restraining ribs to improve rib uniformity andreinforcement.

Shear rate can have a significant effect on oscillation amplitude if thematerials are shear sensitive. In general, as the shear rate isincreased, localized shear heating occurs and the material behaves asthough it has a lower bending modulus. This causes lower amplitudeundulation. This may be partially offset by reducing die temperatures.

Extrusion temperature can range from 130° C. for certain grades ofpolyvinyl chloride and polyethylene copolymers to over 270° C. forhigher temperature materials such as nylon and high molecular weightpolyethylene. Care must be taken to remain above the crystallizationpoint of crystalline materials, especially if they are of the lower meltviscosity. Although horizontal collection techniques are possible, thistechnique is dependent upon melt strength. If the polymer melt strengthis low, then the structure may collapse upon itself immediately uponexiting the die. In this case, vertical collection into a rapidquenching system is necessary.

The collection and quenching system is quite important in the controland production of the wavy rib structure as described herein. The choiceof collection technique is partially determined by the material to beextruded. If the melt possesses a low viscosity or poor melt strength,then a rapid quench into water may be needed. If the melt possesses ahigh viscosity or high melt strength, horizontal extrusion onto a movingbelt carrier with either type of cooling would be adequate. FIGS. 2 and3 illustrate two of the more easily achieved quenching techniques. Toprevent excessive drawdown under the extrudate weight and also to ensureuniform undulation and amplitude, the quench medium should be locatedrelatively close to the die face. The actual distance is dependent uponthe size and amplitude of the undulating rib element. The small sizesare preferably collected very close to the die face, e.g., approximately13mm-25.5 mm, while the large sizes can be quenched further from the dieface, e.g., approximately 25.5-75.5 mm. Enhanced bonding between theundulating rib and any secondary straight rib parallel to and in contactwith the undulating rib is improved if the quench distance is maximized,although this may be difficult if the melt strength is poor.

The final dimensions of the extrudate may also be affected by thecollection technique. If the extrudate is pulled away too rapidly (morerapidly than its natural extrusion rate determined by extruderconditions) its dimensions will generally decrease in proportion and theextrudate is said to be "drawn". Some drawing may be desirable, forspecial effects, but excessive drawing which may straighten the rib andeliminate the undulation should be avoided. Such drawing could reducethe dimension of both the base element and the rib element from thatobtained by extrusion. For this reason, to characterize the amplitude,it is necessary to discuss the conditions under which the extrudate iscollected. The maximum amplitude that may be achieved with the processof the present invention is that amplitude in which the extrudate iscollected under the slowest collection rate or the rate which matchesthe natural extrusion rate of the extrudate determined by extruderconditions. This rate yields an article having ribs with the maximumamplitude permitted by any given die configuration. If the collectionrate is slower than this rate, overall buckling of the extrudate mayoccur which may be undesirable. Hence, it is possible to obtain amaximum amplitude of undulation with any given die configuration. As thecollection rate is increased, articles having ribs with continuallydiminishing amplitudes are produced as the extrudate is drawn.

The cooling structure must be pulled away uniformly to preventpulsations in appearance. This is best done by a pair of nip rollshaving smooth surfaces and gapped to provide a slight compression so asto pinch the structure but not deform the web unduly.

A dual nip set system is particularly preferred when the extrudatematerial is less flexible than a plasticized polyvinyl chloride. In thissituation the upper set of nip rolls are "gapped" to provide a guidingfunction without a positive drive since they must be positioned quiteclose to the die face and yet be under the quench media (typicallywater) when the extruded material is at its softest state and the lowerset of nip rolls are driven to provide a positive pulling influence on acompletely quenched structure at a point where it is no longerdeformable.

In the case of very rigid structures, typically having large dimensions(polypropylene or nylon for example), a vertical collection system ofthe type pictured in FIG. 3 may be necessary since bending or rolling upof the extrudate would be difficult. This collection device consists ofmultiple pairs of nip rolls, appropriately gapped at various locationswith water sprays to quench the extrudate. A sheeting process may beused to cut the structure to convenient and variable lengths since itmay not be easily rolled without damage.

The present invention may be modified by a number of secondaryoperations that may enhance the extrudate. Some examples of usefulsecondary operations include the following:

(a) Lamination of the extrudate. Contacting a secondary material insheet form with the uncured freshly extruded article produces acomposite article. The secondary material could be an adhesive sheet, apolymer film with differing properties or an anti-slip material.

(b) Coextrusion of the article.

The coextrusion technique allows a variation in the method by whichdifferential flow can be achieved, that is by separating the flowbetween the rib and the base element and separately controlling the flowrate to each. It is possible to mix materials to provide ribs of aflexible material and a base element of a rigid material. The variationin material selection may be related to color enhancement, propertyenhancement, or cost benefits.

(c) Embossing of the extrudate is another way of providing a change inthe surface appearance of the article. Embossing a pattern or an edgecan change the physical appearance of the structure, e.g., by adding anedge to the mat structure.

(d) Coating of the extrudate by any of various known techniques (rollcoating, spray coating, dip coating, etc.), the inclusion of otherarticles (carpet strips, flock, abrasive, anti-slip particles, etc.),and curing of the composite may also be employed to change theappearance and/or function of the article.

(e) Incorporation of chemical blowing agents (e.g., azoisocarbonamide)may be used to foam the article with cellular voids to give addedresiliency and/or weight reduction.

Many possible applications exist for this rib structure. The size of theweb selected and the type of material utilized will vary with theapplication desired. Material selection determines whether a rigidstructure or a flexible, rubbery web can be made. The size of thestructure, i.e., rib dimensions and rib spacing influence theappearance, basic weight, and physical properties of the resultant web.The integral rib attached to a base element is especially useful as noadditional binding agent is necessary. Possible applications include: awide variety of matting materials, a geotextile component to promotedrainage (either alone or in combination with other nonwovens), a mediastructure for heat or mass transfer, a substrate for an abrasive fiberor other abrasive article, a spacer material in general, a light ormaterial diffuser, a structural or reinforcing member, a static mixingelement, a handpad or cleaning device, a packing or energy absorbingmaterial, and many decorative items.

EXAMPLES

The following examples are meant to be illustrative, and should not beconstrued as limiting the scope of the invention.

EXAMPLE 1

Polyvinylchloride pellets (Shore A75 hardness) with a melt index of 7(as measured by ASTM 1238 condition E) were melt extruded to produce anarticle having a structure like that of FIG. 12 undulating by using anextrusion die having the following configuration:

    ______________________________________                                        Major rib width  1.27 mm                                                      Major rib height 5.59 mm                                                      Major rib spacing                                                                              6.35 mm                                                      Major rib base   0.46 mm                                                      Minor rib width  0.76 mm                                                      Minor rib height 2.03 mm                                                      Minor rib spacing                                                                              6.35 mm                                                      Minor rib base   0.30 mm                                                      Backing slot     0.46 mm                                                      Static rib width 0.46 mm                                                      Static rib height                                                                              5.59 mm                                                      No. of major ribs                                                                              11                                                           No. of minor ribs                                                                              11                                                           No. of ribs      12                                                           ______________________________________                                    

Extrusion temperatures were in the 150° C. to 165° C. range. Theresulting web was quenched in a water bath at 24.4 mm/second. The basicweight was 2.9 kg/sq. meter. The water level was approximately 25.4 mmfrom the face of the die. A 30 mm extruder was used.

EXAMPLE 2

Plasticized polyvinylchloride pellets (same as in example 1) were meltextruded into an undulating rib structure like that of FIG. 19 using anextrusion die having the following configuration:

    ______________________________________                                               Rib width                                                                              0.76 mm                                                              Rib base 0.46 mm                                                              Rib height                                                                             5.25 mm                                                              Rib spacing                                                                            5.08 mm                                                              Backing slot                                                                           0.46 mm                                                              Wave height                                                                            4.52 mm                                                              Wave radius                                                                            1.22 mm                                                              No. of ribs                                                                            11                                                            ______________________________________                                    

Extrusion temperatures were in the 150° C. to 165° C. range. Theresulting web was quenched in a water bath at 46 mm/second. The basicweight was 3.0 kg/sq. meter. The water level was approximately 25 mmfrom the face of the die. A 30 mm extruder was used.

EXAMPLE 3

Plasticized polyvinylchloride pellets (same as in Example 1) were meltextruded into an undulating rib structure like that of FIG. 15 using anextrusion die having the following configuration:

    ______________________________________                                        Rib width       1.27 mm                                                       Rib base        0.152 mm                                                      Rib height      0.35 mm                                                       Rib orientation 90°                                                    Rib separation  4.72 mm                                                       ______________________________________                                    

Extrusion temperatures were in the 150° C. to 165° C. range. Theresulting structure was quenched in a water bath at 56 mm/second. Thebasic weight was 0.013 kg/sq. meter. The water level was approximately51 mm from the face of the die. A 30 mm extruder was used.

EXAMPLE 4

Commercially available licorice was melt extruded into an undulating ribstructure like that of FIG. 8 using an extrusion die having thefollowing configuration:

    ______________________________________                                        Undulating rib width                                                                            1.12 mm                                                     Undulating rib base                                                                             0.46 mm                                                     Undulating rib height                                                                            4.6 mm                                                     Undulating rib spacing                                                                          6.35 mm                                                     Static rib width  0.46 mm                                                     Static rib height  4.6 mm                                                     No. of static ribs                                                                              5                                                           No. of undulating ribs                                                                          6                                                           ______________________________________                                    

Extrusion temperatures were in the 50° C. to 60° C. range. The resultingweb was air quenched at 1.6 mm/second. The basic weight was 2.96 kg/sq.meter. A 30 mm extruder was used.

What is claimed is:
 1. An article comprising:(a) an elongate baseelement; and (b) at least one elongate rib element having an attachmentend and a free end and being narrower at its attachment end than at itsfree end, said attachment end being attached to said base element alongits entire length, said rib element, at its attachment end, being of thesame length as said base element and, at its free end, being longer thansaid base element and undulated.
 2. The article of claim 1 wherein saidbase element and said rib element are extruded.
 3. An article accordingto claim 1 wherein said article is formed of an extrudable thermoplasticmaterial.
 4. An article according to claim 1 wherein said base element(a) is formed of a first extrudable material and said rib element (b) isformed of a second extrudable material.
 5. An article according to claim1 wherein said article is formed of a synthetic plastic material.
 6. Anarticle according to claim 1 having a plurality of elongate rib elements(b).
 7. An article according to claim 1 wherein said base element isnon-planar.
 8. An article according to claim 7 wherein said articlecomprises a base element having a circular cross-section.
 9. An articleaccording to claim 8 wherein said base element has a solid circularcross-section.
 10. An article according to claim 1 wherein said baseelement is planar and has opposite side edges and first and secondsurfaces.
 11. An article according to claim 10 having at least one ofsaid rib elements attached to each of said first and second surfaces ofthe planar base element.
 12. An article according to claim 10 whereinsaid rib element is attached to said first or second surface of saidbase element at a non-perpendicular angle with respect to the baseelement.
 13. An article according to claim 10 comprising a plurality ofrib elements wherein at least one of said rib elements has an angle ofattachment not equal to the angle of attachment of at least one other ofsaid rib element with respect to the base element thereto.
 14. Anarticle according to claim 1 further comprising at least one secondaryrib element having an attachment end and a free end with said attachmentend being attached to said elongate rib element.
 15. An articleaccording to claim 1 comprising a plurality of rib elements (b), atleast one of said rib elements having a height different from the heightof at least one other of said rib elements.
 16. An article according toclaim 1 comprising a plurality of rib elements (b), at least one of saidrib elements having a frequency of undulation different from that of atleast one other of said rib elements.
 17. An article according to claim1 comprising a plurality of rib elements (b), said rib elements havingdifferent amplitudes.
 18. An article according to claim 1 furthercomprising a plurality of straight, parallel extruded elements, saidstraight, parallel extruded elements being interspersed with saidelongate rib elements.
 19. An article according to claim 1 wherein saidrib elements have a hollow core.
 20. An article according to claim 1including an embossed pattern thereon.
 21. An article according to claim1 wherein said article is formed of a ceramic material.
 22. An articleaccording to claim 1 wherein said article is formed of a pulverized ormolten foodstuff.